The present disclosure relates to nitride semiconductor devices, and more particularly, relates to a nitride semiconductor device including a buried current confining layer.
Currently, much attention has been given to group III-V nitride compound semiconductor, i.e., so-called nitride semiconductor, typified by gallium nitride (GaN), having a chemical formula BwAlxInyGazN (where 0≦w, x, y, z≦1 and w+x+y+z=1). Specifically, nitride semiconductor is formed of boron (B), aluminum (Al), gallium (Ga) and indium (In) which are group III elements, and nitride (N) which is a group V element.
For example, light emitting diodes (LED) employing nitride semiconductor have been used for large display devices, traffic lights, and the like. Also, white LEDs which use a combination of an LED employing nitride semiconductor and a phosphor have been already commercialized, and are expected to be used to replace currently used illumination devices in future, if the luminous efficiency of white LEDs is improved.
With the increasing development of blue-violet semiconductor laser diodes employing nitride semiconductor, the market size thereof grows each year. In a blue-violet semiconductor laser diode, the diameter of a beam spot on an optical disc can be reduced, compared to semiconductor laser diodes emitting light in the red range and the infrared range, used for optical discs such as known CDs, DVDs and the like. Thus, the memory density of optical discs can be increased.
Gallium nitride materials have excellent physical properties, i.e., a high dielectric breakdown electric field, a high saturated drift velocity for electrons in a high electric field, and a high density of two-dimensional electron gas at a heterojunction. Thus, gallium nitride materials are regarded as one of promising materials for electronic devices.
To fabricate a semiconductor device such as an optical device, an electric device or the like, employing nitride semiconductor, a technique for forming nitride semiconductor into a desired shape is required. To form a current confining structure of a laser diode, a gate recess of a FET and the like, a nitride semiconductor layer has to be selectively etched. In general, dry etching is used for etching nitride semiconductor (see, for example, the specification of Japanese Patent No. 3464991).